Solid fuel coatings



United States Patent Office 3,337,312 Patented Aug. 22, 1967 3,337,312SOLID FUEL COATINGS Tibor George Perlus, Toronto, Ontario, Canada,assignor to Douglas Louis Breithaupt No Drawing. Filed Dec. 9, 1963,Ser. No. 329,261 2 Claims. (Cl. 44--6) This application is acontinuation-in-part of my application Ser. No. 75,936 filed Dec. 15,1960, now abandoned.

This invention relates to a coating for solid carbonaceous fuels andmore particularly to a readily ignitable coating which on burningignites the coated fuel. The coating is especially suitable for solidcarbonaceous fuels in small pieces or lumps such as charcoal or charcoalbriquettes which are employed for cooking foods over an open fire suchas with barbecue equipment.

The use of solid carbonaceous fuels for general heating or cookingpurposes is well known and more recently charcoal briquettes and thelike have been used for cooking foods, such as meats, either indoors oroutdoors. The principal difliculty encountered in using charcoal andother solid carbonaceous fuels in lump or briquette form is that theyare not easily ignited and require a more readily combustible materialto ignite them. Liquid starting fuels such as, for example, theso-called lighter fluids, are currently in common usage for ignitingsolid fuels. But, the lighting technique is both laborious andinconvenient and the fluids are dangerous when used without great care,owing to their highly flammable and flame producing characteristics,especially in view of the large quantities that are required to ignitethe solid fuel. Moreover, such fluids generally are expensive andusually burn with an unsavory smell or taste which is often imparted tothe foods being cooked.

Various means have been proposed to kindle solid fuels to overcome thedisadvantages of using lighter starter fuels.

U.S. Patent No. 741,728, Oct. 30, 1903 to Shimper teaches the use of anoxidizing agent, potassium nitrate, and other additives which are mixedintimately with a large proportion of ground charcoal and then pressedinto briquettes. However, the fuel does not provide desirable burningcharacteristics. The oxidizing agent in the proportion taught, beingdispersed throughout the body of the fuel, does not reduce the ignitingpoint of the fuel enough to provide easy kindling. Also the presence ofthe oxidizing agent throughout the body of the fuel results in rapidburning after ignition providing higher temperatures than desired forcooking and reduced burning time for the fuel. The presence of thepotassium nitrate throughout the fuel body during burning results inunpleasant nitrous fumes being evolved and also contamination of thefood.

U.S. Patent No. 1,983,560, Dec. 11, 1934 to Palmer discloses the use offire kindling briquettes to ignite a solid fuel. Such briquettes aredesigned for use with conventional fuels such as coal or coke forstarting an ordinary furnace or grate fire. However, these briquettes donot provide the advantage of igniting the fuel evenly and fully over theentire surface of the fuel to provide the even heating desirable forcooking.

It may be suggested that the briquettes of the Palmer patent be used asthe fuel per so. However, as these briquettes contain the oxidizingagent, sodium nitrate, dispersed throughout the fuel body in a largeproportion they would burn rapidly and provide high temperatures whichare undesirable for cooking. The ingredients of rosin, pitch and lightfuel oil in the fuel body will also make the fuel unsatisfactory forcooking because of the odorifer-ous fumes produced which would be pickedup by the food.

As an alternative other proposals involve solid fuels which have beencoated or impregnated with another material.

U.S. Patent No. 2,822,251, Feb. 4, 1958 to Swinehart et a1. relates to acharcoal briquette coated with a pigmented and plasticized water solublecellulose ether composition in order to provide a clean, dustless, andn0nsmudging fuel. However, although the burning characteristics may beimproved, the coating will not provide a very readily ignitable fuel. Inorder to provide enough heat to raise the temperature of the briquetteto its ignition point a very thick coating of cellulose ether would berequired. Thus, the expense of using this coating is relatively great.

U.S. Patent No. 2,916,364 to Grimes describes a combustible coating inpartially gelled form of a petroleum fraction and an aluminum soap. Sucha coating is highly inflammable and is thus very dangerous and in thisrespect does not overcome the disadvantages of using the liquid startingfuels as described above.

U.S. Patent No. 2,948,594, Dec. 10, 1957, to Doyle deals with a feltedfibrous pulp coating to provide a selfstarting and clean briquette.However, a very large quantity of fibrous pulp would be required toprovide a high enough temperature to ignite the fuel core. It is thusexpensive to provide such a heavy coating. Such a coating will alsoproduce undesirable flames when ignited. It has been foundexperimentally that four times the theoretical quantity of priming fuel,such as proposed by Doyle and Swinehart, is needed to provide enouglrheat to ignite the briquette. For example, if calculation shows that1,000 B.t.u.s are needed to raise the temperature of the surface of thebriquette to its ignition point, enough coating will be needed, inpractice, to supply 4,000 B.t.u.s.

U.S. Patent No. 2,816,013, Dec. 10', 1957 to Powell discloses a coatedand impregnated charcoal fuel body obtained by impregnating a charcoalbriquette with an ordorless mineral spirit and coating the impregnatedbriquette with an organic polymerized material such as cellulosenitrate. In essence, Powell is coating a commonly used lighter fluid(mineral spirit) so that the fluid will not be exposed to atmosphereprior to use. The coating could be considered as a retainer for thelighter fluid. Lighter fluids, as described above, have mnydisadvantages whether they are sprayed on before ignition or impregnatedas taught by Powell. Such fluids are highly flammable and are thus verydangerous. Large quantities of fluid are required to provide enough heatto ignite the fuel. Also there would be a fire hazard during storing orhandling as the mineral spirits would evaporate into the atmosphere ifthe retainer'or coating is broken.

An object of the present invention is to provide a fuel coating which iscapable of being ignited by a burning match, lighter or other commonmeans and which ignites the solid fuel.

A further object is to provide a relatively inexpensive coating whichmay be simply and readily prepared and applied to a solid carbonaceousfuel.

A still further object is to provide a coating characterized by beingnon-toxic, dustless and substantially nonvolatile thereby permittingclean and safe handling, storing and packaging of the fuel.

A still further object of this invention is to provide a solid fuelcoating which will not produce any objectionable odours or appreciableflame or smoke. The coating will also not appreciably affect the cookingor heating qualities of the solid fuel as the solid fuel core will notburn more rapidly or at higher temperatures than normal and the coatingwill not impart any unsavory smell or taste to foods being cooked.

A still further object is to provide a solid fuel coating which ignitesthe solid fuel evenly and fully so that initial combustion takes placeover substantially the entire uppermost layer of the fuel to provide theeven heating desirable for cooking.

The foregoing features and others which will become apparent from areading of this specification, are obtained by a coating prepared inaccordance with my invention which essentially comprises a mixture of acombustible film-forming material and a combustion-supporting oxidizingagent. Although the coating is suitable for solid fuels in either lumpor briquette form, the following description will be directed tocharcoal briquettes for the purpose of explaining the same but notlimiting the scope of the invention thereto.

The coating is simply prepared by adding the film-forming material andthe oxidizing agent to a volatile vehicle in which the oxidizing agentis soluble to form a liquid composition which may be applied to the fuelby any desired manner. Dipping the charcoal briquettes in the liquidcomposition or spraying the briquettes with the composition are examplesof two methods of application which may be employed. Of course, in thecase of the coating ingredients being insoluble in the vehicle, it isnecessary that the composition be agitated during the application to thebriquette to maintain the coating particles in dispersed and suspendedform. Alternately, the solution of oxidizing agent may be applied in onestep and the filmforming material in a second step. After the briquettehas been coated it is dried, usually by heating, to solidify the coatingthereon.

The volatile vehicle may be any liquid which will permit application ofthe coating. Water is especially suitable for this purpose.

The film-forming material to be used for the coating may be any materialwhich is film-forming, combustible, and has the necessary properties toprovide the desired coating. Such materials may be methyl cellulose,starch, or etherified polymeric carbohydrate. It is desirable that thefilm-forming material possess a strengthening and binding-like qualityso that the coating will not be susceptible to crumbling or chalkingthereby preventing the formation of dust.

The use of an oxidizing agent on the surface of the solid fuel is theremarkable aspect of my invention. No one has previously proposed theuse of an oxidizing agent in this way. The Shimper and Palmer patents,discussed earlier, show the use of oxidizing agents dispersed throughoutthe solid fuel body and have the accompanying disadvantages. The Powellpatent discloses the use of cellulose nitrate in a coating and indicatesthat this renders the coating more flammable. However, this is not anoxidizing agent and is not taught to be such by Powell. A calculationwill show that cellulose nitrate C H O (NO does not contain enoughoxygen for its own combustion therefore cannot cause the oxidation ofanother substance and is not an oxidizing agent. If cellulose nitrate ismixed with another combustible material and is ignited, the combustionof the combustible material will not be furthered because of anyoxidation action of the cellulose nitrate but, due to the heat evolved,by the auto-oxidation of the cellulose nitrate the temperature is raisedto a high enough level allowing the combustible compound to combine withthe oxygen of the ambient air.

Examples of suitable oxidizing agents for use in the present inventionare potassium nitrate and sodium nitrate but it should be evident thatmany oxidizing agents, that is chemical compounds containing excessoxygen which is available for reaction with a combustible compoundduring combustion and having the desired properties would be suitable.The oxidizing agent supports and promotes the combustion of the coatingand the uppermost layer of the briquette. The agent together with theoxygen of the ambient air permits the easy ignition and complete combustion of the film-forming material.

Enough heat is evolved during the combustion of the film-formingmaterial to raise the temperature of the outer layer of the briquette tothe ignition-point, which has been lowered significantly by the highproportion of oxidizing agent absorbed into the surface. The combustionof the oxidizing agent impregnated outer layer will in turn ignite thefuel core which will provide the slow, even and substantially odorlessheating desirable for cooking and normally obtained from untreatedfuels. The high proportion of oxidizing agent contained in the coatingand the outer layer of the solid fuel will substantially reduce thequantity of igniting fuel required by the previously proposed treatedfuels. As these igniting fuels are generally expensive the cost isconsiderably reduced by the present invention. Also, as the oxidizingagent of this invention is applied only at or near the surface of thefuel the total quantity required to lower the ignition point of thesolid fuel is much less than would be needed if the oxidizing agent weredispersed throughout the entire fuel body as previously proposed. Thequantity of oxidizing agent to be used will depend on the amountrequired to supplement the ambient air for complete combustion. However,care must be exercised in practicing this invention, to avoid using anamount of oxidizing agent which approaches that required to producecombustion of the coating and the uppermost layer of the briquettewithout the oxygen of the ambient air. The use of too much oxidizingagent will result in an explosive mixture.

A powdered combustible material which will provide texture andadditional heating value to the coating may also be incorporated in thecoating. Carbon black or charcoal in a finely divided state are examplesof such materials, the use of which will reduce the quantity offilmforming material since the heating value of such substancesmaterially assists in raising the briquette to its ignition temperature.

Combustible fibrous materials may also be employed beneficially in thecoating since such materials reinforce the coating and impart porositythereto which allows permeation of ambient air. Such materials includecellulosic fibers, wood particles, e.g. sawdust, or like materials.

An important feature of the coating of this invention is that it has agreater speed of combustion than untreated charcoal thereby producing aglowing zone which will propagate faster on the surface of the charcoalthan on untreated charcoal. The coating provides a full covering of thesolid fuel so that the briquette is ignited evenly and throughout itssurface layer whereby a more even and faster distribution of heat isproduced than in the case of kindlings, or coating or impregnatingmaterials used heretofore.

Another feature of the coating of this invention is that it is non-toxicand therefore can be safely handled by persons. This is particularlyimportant when the fuels are accessible to children.

The coating of the present invention may be readily ignited from thedirect application of a single burning match and will burn with aninsignificant amount of flame or obnoxious odor. Unlike the so-calledlighter fluids and other flammable materials which burn with a flame,the coating minimizes the production of combustible gases and burns withsubstantially no flame and thus reduces fire hazards and the danger ofburns to persons, especially children. This danger is particularlyimportant when the fuel is ignited outdoors so that flames may be blownabout by the wind. Moreover, complete burning of the coating resultswithout appreciably affecting the cooking or heating characteristics orproperties of the briquette and without imparting any unsavoury smell ortaste to foods. The coating with the oxidizing agent is applied only atthe surface where it is needed and having served the purpose of ignitingthe fuel is no longer present. All the igniting coatings, previouslyproposed, are combustible materials which heat up the surface of thesolid fuel whereas this invention provides a material which forms a fastburning fuel on the surface comprising solid fuel and an oxidizing agentwithout changing the properties of the main fuel body.

The present invention is exemplified by the following examples which arenot intended as limiting thereon.

Example 1 uninterrupted surface coating. Drainage of the excesscomposition was allowed and the briquettes were dried at 110 C.

Example 2 12 g. of laundry starch were cooked at 90-95 C. in 300 g.water until opalescence only was observed. A mixture of 12 g. ofcellulose fibers, 6 g. carbon black and 7.5 g. KNO was then added whilemaintaining vigorous stirring. The resulting composition was allowed tocool and then applied and dried as in Example 1.

Example 3 12 g. of etherified polymeric carbohydrate were cooked at90-95 C. in 300 g. water until opalescence only was observed. A mixtureof 12 g. of cellulose fibers, 6 g. carbon black and 7.5 g. KNO was thenadded while maintaining vigorous stirring. The resulting composition wasallowed to cool and then applied and dried as in Example 1.

Example 4 A mixture of 3 g. methyl cellulose, 25 cps. and 3 g.

methyl cellulose, 400 cps. was dissolved in water according to theprocedure of Example 1, 20 g. of soft wood sawdust and 7.5 g. KNO werethen added and dispersed in the aqueous solution. The mixture wasapplied as before.

What I claim as new and desire to protect by Letters Patent of theUnited States is:

1. A barbecue fuel comprising, in combination, a charcoal core having amember selected from the group consisting of potassium nitrate andsodium nitrate absorbed into its surface and a porous skin surroundingsaid surface consisting essentially of a mixture of combustiblefilmforming material selected from the: group consisting of methylcellulose, starch and etherified polymeric carbohydrates, combustiblecellulosic fibres and an oxidizing agent selected from the groupconsisting of potassium nitrate and sodium nitrate present in an amountsufficient on ignition of the coating to supplement ambient air toefiect ignition of the surface of the core.

2. A barbecue fuel according to claim 1 in which the mixture is formedof substantially equal portions of the film forming material and thefibres.

References Cited UNITED STATES PATENTS 741,728 10/ 1903 Shimper 44-171,983,560 12./1934 Palmer 44-41 2,816,013 12/1957 Powell 44-41 2,822,2512/1958 Swinehart et a1. 44-41 2,916,364 12/1959 Grimes 44-41 X 2,948,5948/1960 Doyle 44-6 DANIEL E. WYMAN, Primary Examiner. C. F. DEES,Assistan Examiner.

1. A BARBECUE FUEL COMPRISING, IN COMBINATION, A CHARCOAL CORE HAVING AMEMBER SELECTED FROM THE GROUP CONSISTING OF POTASSIUM NITRATE ANDSODIUM NITRATE ABSORBED INTO ITS SURFACE AND A POROUS SKIN SURROUNDINGSAID SURFACE CONSISTING ESSENTIALLY OF A MIXTURE OF COMBUSTIBLEFILMFORMING MATERIAL SELECTED FROM THE GROUP CONSISTING OF METHYLCELLULOSE, STARCH AND ETHERIFIED POLYMERIC CARBOHYDRATES, COMBUSTIBLECELLULOSIC FIBRES AND AN OXIDIZING AGENT SELECTED FROM THE GROUPCONSISTING OF POTASSIUM NITRATE AND SODIUM NITRATE PRESENT IN AN AMOUNTSUFFICIENT ON INGNITION OF THE COATING TO SUPPLEMENT AMBIENT AIR TOEFFECT IGNITION OF THE SURFACE OF THE CORE.